A total of 59 diploid Aegilops tauschii Coss . (syn . Aegilops squarrosa auct . non L .) and 39 synthetic hexaploid wheat accessions were evaluated for reaction to Pyrenophora tritici-repentis (Died .) Drechs . in a controlled environment, and classified using a disease rating system based on lesion type . 27 Ae . tauschii and 20 synthetic wheats were found to be resistant to tan spot disease . The overall mean disease ratings of Ae . tauschii and the synthetic wheat lines scored on a scale of 1 (resistant) to 5 (susceptible) were 1 .80 and 2 .38, respectively. Synthetic wheats generally showed a decrease in resistance, although several lines of synthetic wheat expressed a higher resistance than the diploid parents . Five synthetic wheat lines exhibited higher resistance than the standard resistant common wheat cultivar `Red Chief' .

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In the course of a Fusarium Monitoring for winter wheat in Bavaria five deoxynivalenol risk factors have been identified. The major Fusarium species wasF. graminearum, which usually has one disease cycle; under specific weather conditions obviously a bicyclic spread of the pathogen occurs.

The need to cut costs has led to a simplification of crop rotation in several fields of plant cultivation. The results of Thormann, who has grown wheat continuously on parts of his farmland for 10 years, are discussed. Also, the preliminary results of our own experiments with increasing proportions of wheat and barley suggest that more wheat and barley may be cultivated in crop rotation than is allowed according to the conventional limits determined by the increase of foot rot diseases and cereal root eelworm. Even in successive crops of maize the problem of soil‐borne pathogens can be tackled: the spread of blister smut is stopped by the control of the frit fly and by selection of tolerant varieties; root and stem rots of maize are overcome by the selection of appropriate varieties, too. On the contrary, the potato root eelworm is a serious pest in all sites of intensive potato production. Only an integrated control including the use of resistant varieties and the application of nematicides gives success. Much research work has to be done mainly to get more information on the biotical defence mechanisms of the soil.

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